Pressure-compensated flow control valve

ABSTRACT

A CONTROL VALVE ASSEMBLY FOR CONTROLLING A TWO-WAY HYDRAULIC CYLINDER INCLUDING A PRESSURE-COMPENSATED FLOW CONTROL VALVE FOR MAINTAINING A CONSTANT PREDETERMINED FLOW RATE TO THE HYDRAULIC CYLINDER, A PAIR OF CHECK VALVES FOR PREVENTING THE RETURN OF FLUID FROM THE ENDS OF THE HYDRAULIC CYLINDER, A PAIR OF OPPOSED HYDRAULICALLY-OPERATED PISTONS RESPONSIVE TO FLUID PRESSURE BETWEEN THEIR FACES FOR RESPECTIVELY ENGAGING AND UNSEATING THE CHECK VALVES AND A MANUALLY-OPERATED SPOOL-TYPE DIRECTION CONTROL VALVE FOR SELECTIVELY CONNECTING THE OUTLETS OF THE PRESSURE-COMPENSATED VALVE TO ONE OR THE OTHER OF THE ENDS OF THE HYDRAULIC CYLINDER AND TO THE FACES OF THE OPPOSED PISTONS.

United States Patent [72] Inventors Donald James Parquet Dike; Daniel Luce Hall, Waterloo, lowa [2l] Appl. No. 821,184 [22] Filed May 2,1969 [45] Patented June 28,1971 [73] Assignee Deere & Company Moline, Ill.

[54] PRESSURE-COMPENSATED FLOW CONTROL VALVE 6 Claims, 1 Drawing Fig.

[52] U.S. CI 137/504 [51] Int. Cl G05d 7/01, F 16k 1/44 [50] Field of Search 137/504,

`[56] References Cited UNITED STATES PATENTS 1,044,053 ll/l9l2 Huxford 137/503 1,159,214 ll/l9l5 Gueux 137/503 2,917,075 12/1959 Terry 137/504 3,120,243 2/1964 Allen etal. 137/504 3,156,258 l H1964 Moody 137/504 3,421,542 1/1969 Adams et al. 137/504 3,464,439 9/1969 Budzich. 137/504 Primary Exam ner-M, Cary Nelson Assistant Examiner-Robert J. Miller Attorneys-H. Vincent Harsha, Harold M. Knoth, William A.

Murray, John M. Nolan and Jimmie R. Oaks ABSTRACT: A control valve assembly for controlling a twoway hydraulic cylinder including a pressure-compensated ow control valve for maintaining a constant predetermined flow 7 ||l|| im PATENTEU M28 1971 NVENTORS D. J. PARQUET a D. L. HALL ATTORNEY PRESSURE-COMPENSATED FLOW CONTROL VALVE BACKGROUND OF THE INVENTION This invention relates to an improved pressure-compensated flow control valve assembly and more specifically relates to a pressure-compensated valve assembly which is particularly useful in hydraulic systems for controlling the operation of hydraulic cylinders or motors.

Hydraulic cylinders are often subjected to a wide range or loads when used in certain applications. One such application, for example, is the lift cylinders for front end loaders. It is desirable for predictable and safe operation to have the front end loader bucket raise at a constant speed regardless of the load and it is also desirable to be able to tilt the loader bucket without a pressure loss in the lift cylindercausing the bucket to drop. lt is known that these desired operations can be accomplished by the provision of a pressure-compensated flow control valve between the source of pressurized fluid and the lift cylinder and by placing a check valve between the flow control valve and lift cylinder, However, such previously known valves have had at least one of the faults of being too complicated, unreliable, or nonadjustable. Also, in prior systems, the check valves have been provided separate from the pressure-compensated flow control valve.

SUMMARY OF THE INVENTION According to the present invention, there is provided for use in a hydraulic system for controlling a hydraulic function, an improved pressure-compensated flow control valve assembly for maintaining a predetermined flow :rate regardless of the system pressure. l

More specifically, it is an object of this invention to provide a pressure-compensated flow control valve assembly which includes only three major components namely, a spring, flow regulating valve member and a flow control valve member mounted coaxially within the flow regulating valve member.

Another object is to provide a flow regulating valve member and a flow control valve member which cooperate to define an orifice, the flow control valve member being adjustable to change the size of the orifice for selecting a desired flow rate.

A further object is to provide a pressure-compensated flow control valve assembly, including a flow regulating valve member and a flow control valve member, which cooperate to function as a check valve to prevent reverse flow.

Another object is to provide a pressure-compensated flow control valve assembly so constructed that components thereof remain in a working attitude, thus providing reliable operation.

Still another object is to provide a pressure-compensated flow control valve assembly which is compact, adjustable without disassembly, easily installable and economical.

These and other objects will become apparent from the following description and the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The sole FIGURE illustrated is a combined sectional and schematic view of the hydraulic system in a neutral condition, showing the pressure-compensated flow control valve assembly and pilot-operated check valve assembly in section and schematically showing the remainder ofthe system.`

DESCRIPTION OF THE PREFERRED EMBODIMENT The hydraulic system includes a hydraulic motor control valve assembly having a valve body 22 and a pressure-compensated flow control valve assembly 24 having a valve body 25.

A representative hydraulic function 26, here shown as a double-acting hydraulic cylinder or ram, includes a cylinder 28 and a piston 30 movable in the cylinder in response to a pressure differential between the opposite ends 32 and 34 of the cylinder.

One end 32 of the cylinder is connected to a first motor outlet passage 36 in the body 22, by a conduit 38, and the other end 34 of the cylinder is connected to a second motor outlet passage 40 by a conduit 42.

The first and second motor outlet passages 36 and 40 are intersected by a cylindrical bore 44 extending through the body 22 and closed at opposite ends by end caps 46 and 48 respectively` The bore 44 is also intersected between the first and second motor outlet passages 36 and 40 by first and second passages 50 and 51. A first valve seat 52 having an axial orifice 53 is mounted in the bore 44 between the first motor outlet passage 36 and the passage 50 and a second valve seat 54 having an axial orifice 55 is mounted in the bore 44 between the second motor outlet passage 40 and the passage 51. The first motor outlet passage 36, the passage 50 and the valve seat 52 form a first passage means or conduit means through the body 22 closable by a spherical check valve 56 biased against the valve seat 52 over the orifice 53 by a spring 58 acting between the end cap 46 and the check valve 56 for preventing the return of fluid from the motor outlet passage 36 to the passage 50. Similarly, the second motor outlet passage 40, the passage 51 and the valve seat 54 between the passages form a second passage for conduit means through the body 22, closable by a check valve 60 biased against the valve seat 54 over the orifice 55 by a spring 62 acting between the end cap 48 and the check valve 60 for preventing the return of fluid from the second motor outlet passage 40 to the passage 51.

The bore 44 is closed between the passages 50 and 5l by a pair of cylindrical members 64 and 66 mounted in the bore adjacent the passages 50 and 51 respectively. A third passage 68 extends between the members 64 and 66. A pair of pistons 72 and 73 are slidable in the bore 44 between the check valves 56 and 60, the pistons having opposite radial faces 74 and 75 recessed to form a chamber 76 to which the passage 68 is connected. The pistons have reduced diameter axial shaft portions 77 and 78, which extend through the cylindrical members 64 and 66 respectively and have axial conduits 80 and 82, which respectively connect the chamber 76 to the first 'and second passages 50 and 51. Valve seats 84 and 86 are respectively located in the conduits 80 and 82, and a pair of spherical check valves 88 and 90 are respectively positioned for engagement with the seats 84 and 86 to allow flow only from the first and second passage means to the chamber 76. The check valves 88 and 90 are held adjacent the respective seats by a pair of retainer washers 92 and 94 respectively. The axial shaft portion 77 and 78 of the pistons respectively engage and unseat the check valves 56 and 60 when the chamber 76 is pressurized enough to overcome the fluid pressure and spring forces exerted on the check valves. To insure free movement of the pistons, the space between the pistons 72 and 73 and the associated cylindrical members 64 and 66, is connected to the reservoir via a pair of passages 96 and 98 respectively.

A spool-type direction control valve 100, shown schematically in the drawing, has two pressure inlet ports 102 and 104 and an exhaust port 105, connected to a fluid reservoir 106. The valve is manually shiftable into four alternate positions, establishing different connections between the inlet and exhaust ports and the passages 50, 68 and 51.

The pressure-compensated flow control valve assembly 24 includes a generally cylindrical bore 108 formed in the valve body 25. The bore 18 is transversely intersected by an inlet passage 110 and outlet passages 112 and 114, which are respectively connected to the inlet ports 102 and 104 of the direction control valve by means of conduits 116 and 118. Conduit 118 contains a check valve 120 for allowing flow only from the passage 114.

The pressure-compensated flow control valve assembly 24 maintains a constant preselected flow between the inlet port and the outlet ports 112 and 114 and includes a compression spring 122, which acts between the respective right ends of the bore 108 and a tubular or sleevelike regulating valve member 124 and governs the normal operating pressure drop across the valve member 124 as will be fully explained below.

The regulating valve member 124 extends across the inlet 110 and contains a plurality of radially extending ports 126, which cooperate with the inlet 110 to meter flow into the valve member 124, the amount of metering depending on the axial position of the ports 126. The regulating valve member also has an interior annular shoulder 128 located slightly downstream from the ports 126.

A flow control valve member 130 is positioned within and in concentric relationship to the regulating valve member 124 and includes a cylindrical portion 132, terminating in an annular shoulder 134, which is opposite to and forms a seat for the shoulder 128 of the regulating valve member 124, the shoulders functioning as a check valve to prevent reverse flow through valve member 124. A tapered end portion 136 extends from the shoulder 134 and cooperates with the regulating valve member 124, when the valve member 124 is shifted to the right from the position illustrated, to provide a variable orifice. A stem 138 having a threaded portion 140 extends from the left end of the cylindrical portion 132 through an internally threaded end closure member 142 to provide means for axially adjusting the control valve member 130. The valve member is held in a selected position by means of a lock nut 144.

Each adjusted position of the valve member 130 will result in a different flow rate and this preselection of flow rate is made possible due to the fact that through the range of normal operating pressures, -pressurizing the left end of the valve member 124 will shift it to the right to approximately the same axial position. Stated otherwise, only a small increment of axial movement of the valve member 124 is necessary to compensate for the system pressure changes developed during ordinary operation and because of the gradualness of the taper of the portion 136, these small increments of axial shifting will only slightly change the size of the orifice defined between the valve members 130 and 124. Thus, the flow rate through the orifice will be disturbed only a negligible amount and the pressure compensation can, for all practical purposes, be considered as occurring only between the inlet 110 and the radial ports 126. Since the orifice size remains substantially the same during operation for a selected axial position of the valve member 130, the flow permitted through the orifice will be substantially constant and to change flow rates it is necessary only to select a different axial setting for the valve member 130. The gradualness of the taper of the portion 136 makes possible a relatively fine flow rate adjustment.

The inlet 110 of the bore 108 is connected to a source of fluid under pressure 150 by means of conduit 152, the source of fluid under pressure being connected to the reservoir 106 by means of a conduit 154.

An auxiliary function 156 in the form ofa two-way hydraulic cylinder of conventional construction is selectively actuated in opposite directions by selective actuation of a manually operated direction control valve 158, adapted to connect one end of the cylinder to the pressure source 150 and the other end to the reservoir 106.

ln operation, assuming that the system is fully charged and in the neutral condition illustrated, there will be no flow except for ordinary leakage between the inlet 110 and the outlets 112 and 114 of the bore 108.

If it is desired to raise a load by operation of the two-way cylinder 26, the direction control valve 100 is manually shifted to the left from the neutral position illustrated to connect the pressure port 102 to the passage 5l and the pressure port 104 to the passage 68 and the associated chamber 76.

Upon shifting the direction control valve to the left as described above, pressure ofthe right end of the regulating valve member 124 will decrease and fluid pressure at the left end of the regulating valve member 124 will shift the regulating valve member to the right, against the bias of the spring 122, to a position wherein only a small portion of the radial ports is exposed to the inlet 110, which position is approximately the same for all normal operating pressures. ln this position, the shoulder 128 of the valve member 124 will be annularly spaced form a point along the tapered end portion 136 of the valve member to define an orifice the size of which may be preselected by turning the threaded portion of the flow control valve member to axially shift the tapered end portion 136. Flow then will be permitted between the inlet 110 and the outlets 112 and 114 via the radial ports 126 and the orifice. Flow through the orifice is restricted and results in a pressure drop across the valve member 124. the valve member 124 having its left and right ends exposed to the fluid pressure to the left and right of the orifice respectively. When the valve member 124 is in equilibrium, the pressure drop across the ends of the valve member 124 plus flow forces will equal the force exerted by the spring 122. ln other words, the fluid pressure exerted on the left end of the valve member 124 will equal the fluid pressure plus the spring force exerted on the right end.

The flow rate through the preselected orifice will remain constant as long as the pressure drop across the orifice is constant and the function of the regulating valve member 124 is such as to maintain the pressure drop at a constant value. For example, if the pressure drop were to instantaneously increase, as would be the case if the pressure increased at the left of the orifice or decreased at the right of the orifice, the valve member 124 would shift slightly to the right to close the metering space between the radial ports 126 and the inlet 110 an amount sufficient to cause the pressure at the left end of the valve member 124 to decrease and reestablish the desired pressure drop. Similarly, if the pressure drop were to instantaneously decrease, as would be the case if the pressure decreased at the left of the orifice or increased to the right of the orifice, the valve member 124 would shift slightly to the left and open the metering space between the radial ports 126 and the inlet 110 an amount sufficient to cause the pressure at the left end of the valve member 124 to increase and reestablish the desired pressure drop.

Assuming that the cylinder 26 is the lift cylinder of a front end loader and that the auxiliary function 156 is a bucket tilt cylinder and that it is desired to tilt the bucket while the bucket is being raised without returning the direction control valve 100 to the neutral position, the manually operated direction control valve 158 is shifted to pressurize one or the other of the work ports of the cylinder 156 while connecting the other end to the reservoir. The operation of the tilt cylinder 156, which operates at a much lower pressure than the lift cylinder 26, will result in a decrease of pressure available for operating the lift cylinder 26 land the load on the cylinder 26 will attempt to force fluid reversely through the pressure port 102 and reversely through the outlet 112 of the pressure-compensated valve assembly 24. Such reverse flow is prevented since the change in pressure caused by diverting flow to the function 156 will cause the shoulder 128 of' the regulating valve member 124 to seat against the shoulder 134 of the flow control valve member 130.

Since the operation of the pressure-compensated valve assembly 24 is essentially the same for other operations of the hydraulic actuator 26, no further description is thought necessary.

While the preferred embodiment of the invention has been shown and described, it will be apparent that variations and modifications thereof may be made without departing from the underlying principles thereof.

We claim:

1. A pressure-compensated flow control valve assembly comprising: a valve body defining a bore having an inlet and an outlet, a control valve member coaxially mounted within said bore and having at least one portion between said inlet and outlet, a sleevelike regulating valve member slidably mounted within the bore and extending coextensively with said one portion of said control valve member, stop means including an abutment surface on said control valve member for limiting axial sliding movement of the regulating valve member in one direction, bias means urging the regulating valve member toward engagement with said abutment surface,

said regulatingvalve member including edge means operative for increasingly restricting one of said inlet and outlet as said regulating valve member shifts away from said abutment surface, said regulating valve member having a normal operating position away froml said abutment surface wherein it cooperates with said one portion of the control valve member to form an orifice for permitting a predetermined flow rate therethrough at a preselected pressure drop, said regulating valve having its opposite .ends exposed to the respective fluid pressures on the opposite sides of the orifice whereby instantaneous increases and decreases in pressure drop across the orifice will be nullified by the regulating valve shifting, in response to changes of pressures on its opposite ends, respectively away from or toward the abutment surface to respectively decrease or increase the restriction of said one of said inlet and outlet. l

2. The invention defined in claim l wherein said abutment surface is in the form of a shoulder formed annularly about said control valve member at an axial location in said bore between the inlet and outlet and wherein said regulating valve member has a complementary shoulder for seating engagement with said shoulder of said control valve member to function as a check valve for preventing reverse flow through the inlet and outlet.

3. The invention defined in claim 2 wherein the edge means of said regulating valve member includes a plurality of circumferentially spaced ports located substantially midway between the opposite ends of the regulating valve member whereby f'low through the ports will not tend to tip and bind the sliding operation of the regulating valve member.

4. The invention defined in claim 3 wherein said ports of said regulating valve member are positioned to meter llow through the inlet of said bore.

5. The invention defined in claim l wherein the edge means of said regulating valve member includes a plurality of circumferentially spaced ports located substantially midway between the opposite ends of the regulating valve member whereby flow through the ports will not tend to tip and bind the sliding operation of the regulating valve member.

6. The invention defined in claim 5 wherein said ports of said regulating valve member are positioned to meter flow through the inlet of said bore. 

